Outdoor Blue Spaces, Human Health and Well-Being: a Systematic Review Of
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1 Outdoor blue spaces, human health and well-being: a systematic review of 2 quantitative studies 3 4 Mireia Gascona,b,c, Wilma Zijlemaa,b,c, Cristina Verta,b,c, Mathew P. Whited, Mark 5 Nieuwenhuijsena,b,c 6 7 Affiliations 8 aISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de 9 Barcelona, Barcelona, Spain 10 bUniversitat Pompeu Fabra (UPF), Barcelona, Spain 11 cCIBER Epidemiología y Salud Pública (CIBERESP), Barcelona, Spain 12 dEuropean Centre for Environment & Human Health, University of Exeter Medical 13 School, Truro, UK. 14 15 Name and contact of the corresponding author 16 Mireia Gascon 17 Parc de Recerca Biomèdica de Barcelona (PRBB) – ISGlobal (CREAL) 18 Doctor Aiguader, 88 | 08003 Barcelona, Catalonia, Spain 19 Phone: 0034 932147363 Fax: 0034 932045904 20 email: [email protected] 21 22 23 1 33 Abstract 34 Background: a growing number of quantitative studies have investigated the potential 35 benefits of outdoor blue spaces (lakes, rivers, sea, etc) and human health, but there is 36 not yet a systematic review synthesizing this evidence. 37 Objectives: to systematically review the current quantitative evidence on human health 38 and well-being benefits of outdoor blue spaces. 39 Methods: following PRISMA guidelines for reporting systematic reviews and meta- 40 analysis, observational and experimental quantitative studies focusing on both 41 residential and non-residential outdoor blue space exposure were searched using 42 specific keywords. 43 Results: in total 35 studies were included in the current systematic review, most of them 44 being classified as of “good quality” (N=22). The balance of evidence suggested a 45 positive association between greater exposure to outdoor blue spaces and both benefits 46 to mental health and well-being (N=12 studies) and levels of physical activity (N=13 47 studies). The evidence of an association between outdoor blue space exposure and 48 general health (N= 6 studies), obesity (N=8 studies) and cardiovascular (N=4 studies) 49 and related outcomes was less consistent. 50 Conclusions: although encouraging, there remains relatively few studies and a large 51 degree of heterogeneity in terms of study design, exposure metrics and outcome 52 measures, making synthesis difficult. Further research is needed using longitudinal 53 research and natural experiments, preferably across a broader range of countries, to 54 better understand the causal associations between blue spaces, health and wellbeing. 55 56 Keywords: outdoor; blue spaces; health; well-being 57 3 58 Introduction 59 A growing body of literature suggests that natural outdoor environments might help 60 reduce stress, promote physical activity and social relationships and potentially improve 61 human health and well-being (Dadvand et al., 2016; Hartig et al., 2014; Nieuwenhuijsen 62 et al., 2017; Pasanen et al., 2014; Völker and Kistemann, 2011). Furthermore, the 63 presence of natural environments in urban settings, particularly green spaces (trees, 64 grass, forests, parks, etc), has been associated with a reduction of the levels of air 65 pollution and noise, as well as extreme temperatures in cities, which can lead to a 66 reduction of the impacts of these environmental factors on our health (Burkart et al., 67 2016; Hartig et al., 2014; Shanahan et al., 2015; Wolf and Robbins, 2015). In a world 68 with rapid urbanization and pressure on space (United Nations Department of Economic 69 and Social Affairs, 2014), evidence of such health benefits of natural environments are 70 of high relevance for healthcare professionals, urban planners and policymakers, who 71 can help translate available evidence into salutogenic interventions and policies (i.e. 72 ones that support and promote health and well-being). 73 74 Most of the studies in this field to date have focused on the health benefits of green 75 spaces, including several systematic and non-systematic reviews (e.g. Dzhambov et al., 76 2014; Dzhambov and Dimitrova, 2014; Gascon et al., 2016, 2015; Kabisch et al., 2015; 77 Lee and Maheswaran, 2011; Nieuwenhuijsen et al., 2017; WHO, 2016). However, 78 fewer studies have focused on the health impacts of outdoor blue spaces, defined in the 79 European Commission funded project BlueHealth (https://bluehealth2020.eu/) as 80 “outdoor environments - either natural or manmade - that prominently feature water and 81 are accessible to humans either proximally (being in, on, or near water) or 82 distally/virtually (being able to see, hear or otherwise sense water)” (Grellier et al., 4 83 2017). Despite a rich and growing body of multi-faceted, qualitative and narrative work 84 that is shedding important light on people’s interactions with blue space environments, 85 including their perceptions of potential health benefits (Foley and Kistemann, 2015; 86 Völker and Kistemann, 2011), we know less about the quantitative, primarily 87 epidemiological data that seeks to address questions such as “Is living near or having 88 better access to blue space environments associated with positive health and well-being 89 outcomes?”. Although one systematic review, focusing on mortality, did seek to explore 90 the relationship with blue space, in addition to more commonly researched green space, 91 no studies were found at that time to have considered this association (Gascon et al., 92 2016). However, we know of far more studies that have looked at blue space and 93 morbidity and well-being outcomes although as yet no systematic review of this 94 literature has been conducted. The aim of the current paper was to fill this gap. 95 Moreover, given that it has been hypothesized that any of the potential benefits to health 96 and well-being from exposure to outdoor blue space may follow pathways similar to 97 those identified for green space including stress reduction, increased physical activity, 98 promotion of positive social contacts, increased place attachment and the reduction of 99 extreme temperatures may also play a role for outdoor blue spaces (Grellier et al., 100 2017), the current review will explore this potential pathways as well. 101 102 Materials and methods 103 Search strategy and selection criteria 104 We followed the PRISMA statement guidelines for reporting systematic reviews and 105 meta-analyses (Moher et al., 2010). The bibliographic search was conducted using 106 MEDLINE (National Library of Medicine) and SCOPUS search engines and keywords 107 related to outdoor blue spaces (blue space, river , lake, sea, beach, fountains, riparian, 5 108 oceans, coastal, marine) combined with keywords related to health and well-being 109 (mood disorder, depressive disorder, depression, anxiety disorder, anxiety, obsessive- 110 compulsive disorder, stress, mental health, mental hygiene, mental disorders, emotional 111 well-being, psychological well-being, social well-being, well-being, cognitive function, 112 health, cardiovascular diseases, heart diseases, blood pressure, hypertension, obesity, 113 overweigh, weight, body mass index, BMI) as well as keywords related to the potential 114 mechanisms accounting for this association (physical activity, social capital, social 115 contacts, social support). The search was limited to the English language and studies in 116 humans and the last search was conducted on July 1st 2016. All studies published prior 117 to that date and that followed the inclusion criteria were included in the systematic 118 review. In order to have a potentially global overview, the country where the study had 119 been conducted was not an inclusion criterion. Two authors (MG and WZ) 120 independently identified and conducted the first screening of the articles based on the 121 information available in the title and abstract by using the Rayyan tool (Elmagarmid et 122 al., 2014), an online tool that provides procedural support in the selection of articles for 123 systematic reviews. After this first screening stage, based on titles and abstracts, both 124 authors independently read each article to decide whether or not these were eligible for 125 inclusion. After this process, authors compared the final list of papers included by each 126 of them and where disagreements or doubts were encountered the final decision was 127 resolved by discussion between the two independent researchers. We also checked the 128 references of the relevant articles and other sources to find additional articles following 129 the inclusion criteria. 130 131 Study eligibility criteria and quality of the studies 6 132 The selection criteria were as follows: a) the article needed to be an original research 133 article, b) all type of study designs were included (ecological, prospective, cross- 134 sectional, case-control, and intervention studies), c) the article used quantitative data to 135 report analysis of health and well-being, social or physical activity outcomes in relation 136 to outdoor blue space exposure, d) outdoor blue space exposure was included as a 137 separate variable within the analysis and results were reported specifically for outdoor 138 blue space, even if this was not the primary aim of the study. 139 140 We extracted the following data: author, year of publication, country, study design, 141 study population, sample size, exposure assessment, outcome assessment, confounding 142 factors, and other relevant information including information on potential biases (Tables 143 1-4 and supplemental material Table A). The data extraction work was conducted by the 144 two authors independently, as well as the evaluation of their quality and classification of 145 the evidence. Agreement was reached via consensus. Study quality evaluation was 146 based on an adapted version of the criteria used in previous reviews in the green space 147 field (Gascon et al., 2016, 2015). Further information on how the quality scores were 148 given is provided in Table B of the supplemental material. The following quality scores 149 (%) were derived as follows (supplemental material Table C): excellent quality (score 150 ≥81%), good quality (between 61 and 80%), fair quality (between 41 and 60%), poor 151 quality (between 21 and 40%) and very poor quality (≤20%).